Recruitment cross-subsidy of snapper from reserves to fished populations

Abstract

The creation of marine reserves can be justified on the basis of scientific value, protection of biodiversity and eco-tourism benefits. However, they still face opposition from fishing interests, who claim that they lock up resources and increase fishing pressure elsewhere. This study uses numerical modelling to investigate the potential for recruitment cross-subsidy (marine reserves replenishing fish stocks outside their boundaries) from the Leigh Marine Reserve, New Zealand. A hybrid 2/3 dimensional hydrodynamic model is used to provide current and tides to a particle tracking model, which simulates the movement of snapper larvae. The model results indicate that wind conditions can significantly affect the direction and extent of snapper larvae dispersal outside the reserve. The complex 3-D dynamics of the eddies near Cape Rodney also play a significant role. The buoyancy of larvae as they develop is also important and more experimental work is required to quantify this. However, under all conditions simulated, modelled snapper larvae were transported large distances from the Leigh Marine Reserve, indicating significant potential for recruitment cross-subsidy.